What is stationary combustion? Scope 1 fuel emissions

Stationary combustion is the burning of fuel in equipment that does not move: boilers, furnaces, ovens, kilns, turbines and backup generators. Under the GHG Protocol Corporate Standard (Revised Edition, Chapter 4), the emissions from fuel burned this way in equipment a company owns or controls are direct emissions, in Scope 1. Its counterpart is mobile combustion, the fuel burned in vehicles and mobile machinery, which is Scope 1 too but a separate source.

Stationary vs mobile combustion#

The IPCC 2006 Guidelines for National Greenhouse Gas Inventories treat the two in separate chapters of Volume 2 (Energy): Chapter 2, Stationary Combustion, and Chapter 3, Mobile Combustion. The CO2 from a litre of diesel is the same in both; the CH4 and N2O are not, which is why a fuel can carry different factors for a boiler and for an engine.

Examples#

• A gas boiler heating an office, a school or a warehouse.
• An oil-fired boiler in a building with no gas connection.
• A gas-fired furnace or oven in a factory or a bakery.
• The fuel burned in a cement or lime kiln.
• A diesel backup generator, or a gas turbine or combined heat and power unit on site.
• A wood-pellet or wood-chip boiler, with the biomass rule below.

What is not stationary combustion#

• Heat, steam or cooling you buy from a network: Scope 2, since someone else burns the fuel. Factors: District heat and steam.
• Electricity you buy: Scope 2, reported two ways, see Market-based vs location-based Scope 2 electricity. Power from your own generator is not Scope 2: the fuel it burns is already in your Scope 1.
• The fuel's supply chain: extracting, refining and transporting the fuel before you burn it is Scope 3 category 3, fuel- and energy-related activities, under the GHG Protocol Scope 3 Standard. See Estimated fuel legs.
• The CO2 from burning biomass: wood, biogas or other biomass. The Corporate Standard has it reported separately, outside the scopes; the CH4 and N2O from that burn stay in Scope 1. See Biogenic carbon, land use and the CO2e basis.
• Leaks and process emissions: gas escaping from a pipe, refrigerant leaking from a chiller, or the CO2 a kiln releases from limestone itself are Scope 1, but they are fugitive or process emissions, not combustion. Factors: Fugitive emissions and refrigerants.

How to calculate it#

Multiply the fuel you burned by a combustion factor for that fuel, in the same unit:

emissions (kg CO2e) = fuel used × emission factor (kg CO2e per unit of fuel)

Match the unit exactly. A factor per kWh on a gross calorific value basis does not apply to kWh on a net basis, and the gap is about 10 % for natural gas; How fuel factors are converted explains the two.

The factors that cover it#

Stationary combustion factors sit in the Fuels category of factor search, in five sub-categories:

A fuel factor's system_boundary says which part of the fuel's life it covers. combustion is the burn alone, the number for Scope 1. upstream_fuel is the supply chain before the burn, for Scope 3 category 3. well_to_use is the two together. Where a publisher prints combustion only, open-climate.ai adds the supply chain and the total as marked estimates (the leg and the total); System boundaries shows how the parts relate.

Three combustion factors from MITECO for Spain, reference year 2025:

A worked example: a gas boiler in Spain#

A company's boiler in Spain burned 50,000 kWh of natural gas in 2025, metered on a gross calorific value basis, the basis of MITECO's factor.

The Scope 1 figure is 50,000 × 0.182 = 9,100 kg CO2e, about 9.1 tonnes. The supply chain adds about 16 % on top, but it belongs in Scope 3, so never add the well_to_use total to Scope 1.

A heating-oil boiler works the same way: 2,000 litres of gasóleo C give 2,000 × 2.898 = 5,796 kg CO2e in Scope 1.

Related#

• Estimated fuel legs: the supply chain before the burn
• How fuel factors are converted
• System boundaries
• Biogenic carbon, land use and the CO2e basis
• Market-based vs location-based Scope 2 electricity